Dissertation > Industrial Technology > Machinery and Instrument Industry > Mechanical parts and gear > Other mechanical components

Finite Element Analysis and Structure Optimal Design for Combined Seal at Normal Temperature and Low Temperature

Author ChenGuoDong
Tutor HouZhenXiu
School Harbin Institute of Technology
Course Mechanical and Electronic Engineering
Keywords combined seal sealing behaviour finite element analysis structure optimal design
Type Master's thesis
Year 2008
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It has highly request in seal’s capability and reliability in liquid rocket engine, because the sealing behaviour would influence the whole system. The combined seal in this subject is a kind of dynamic seal in one rocket engine, consisting of one ptfe sliding ring and one O-ring, requested reliable seal at both normal temperature(20℃) and low temperature(-40℃). Finite element analysis about all work conditions of this sealing structure will help to analyze the sealability in the round, find the weakness, optimize the structure, and improve the reliability, which has great significance.Firstly, material property of ptfe and nitrile rubber is analyzed. Because the mechanics behaviour of rubber can not be described simply by modulus of elasticity, stress and strain datas of nitrile rubber are obtained through experiments at 20℃and -40℃. Using finite element software ANSYS, constitutive equations of nitrile rubber at 20℃and -40℃are established.Finite element model of the combined sealing structure is established. After numerical simulation about static work state and reciprocating work state of combined structure at 20℃and -40℃, the stress field, displacement field and deformation of the combined seal is obtained, analyzing the sealing behaviour in all rounds.Based on hydrodynamic theory and resusts of finite element simulation, film thickness calculated is consistent of that of theory. By the method of drawing graph, distribution of film thickness is ploted. Influencing factors to leakage is analyzed in theory, giving guidances to improve the sealing reliability.Simulator investigation is done to the parameters of work condition and structure which influence the sealing behaviour, finding out how working pressure, compression, front angle, back angle, thickness of sliding ring, and offset form the center of O-ring influence the sealing behaviour. Based on this, the sealing structure is optimized, and results of optimization is obtained.In the end of this paper, the failure modality and the factors influencing sealing performance are discussed. The influence of friction, temperatures, and installation accuracy to the failure of the combined seal is selective analyzed. These researches provide comprehensive information for design of this kind of combined sealing structure.

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